Process and apparatus for coating paper



T. E. KNAPP, JR PROQESS AND APPARATUS FOR COATING PA PER Aug. 29 1933.

Filed NOV. 29, 1930 Patented Aug. zaisas UNITED STATES PROCESS ANDAPPARATUS FOR COATHWG PAPER Theodore E. Knapp, Jr., Hamilton, Ohio,assignor to The Champion Coated Paper Company,

Hamilton, Ohio, a-corporation of Ohio Application November 29, 1930Serial No.

' Claims (CL 9127) This invention relates to a process of coating paperand to apparatus designed to perform said process.

The term coated paper is here used in the 5 sense in which it iscommonly employed in the paper industry, that is to say, paper which hasbeen coated with a fluid suspension of mineral pigment, such as clay,satin white and the like, in an aqueous solution of an adhesive such ascasein, starch and the like, and the'terms coating, aqueous coating,coating mixture, etc., as used herein, are to be interpreted inaccordance with this definition. I

In United States Patent No. 1,774,398 there is disclosed a process andapparatus for coating paper in which the brushes commonly used to smoothand distribute the coating on the paper web or sheet are replacedbymetallic, e. g. steel surfaced rolls, rotating reversely to thedirection of movement of the paper. One objection to this type of coateris that the coated paper so made is marred by ridges in the coatingextending lengthwise of the ridges, under proper operation of thecoater, may not be very heavy, but they are characteristic of coatedpaper so made, and naturally this impairs its use for certain purposessuch as fine half-tone printing where an exceedingly smooth surface isrequired.

The present invention contemplates a coater -in which the difficultiesinherent in the use of reversely turning metallic, e. g. steel smoothingand distributing rolls, are overcome.

The invention will be described by reference to the'accompanyingdrawing.

Fig. 1 is a diagrammatic representation of the essential partsof thecoater;

Fig. 2 is a diagrammatic smoothing rolls.

While the drawing illustrates and the following description refers onlyto cylindrical roll it will be understood that other devices such as atraveling belt might be substituted therefor.

Referring to the drawing, 2 is the web of paper to be coated, suppliedfrom the roll thereof of 1. 3 and 4 are guide rolls, and 5 is asupporting roll around which the paper travels. 6 is a pan of coatingmixture into which the roll '1 dips. 8 is a large rotating brush whichpicks up coating from the roll '1 and deposits it on-the paper as itpasses around the roll 5. The weight of coating so applied to thepapermay be controlled in the well-known manner, as by regulation of therelative speeds of rotation of rolls '7 and 8 and 55 the travel of thepaper web. 9 is an apron travelview of one of the travel of the sheet.These ing on rolls 11 and 12, which serves to draw the paper through themachine. 10, 10, 10, are smoothing rolls driven in the reverse directionto the movement of the paper, preferably at a surface speed greater thanand desirably two or 63 more times that of the paper. 13, 14, 15 and 16are supporting rolls. After contact with these smoothing rolls the paperis carried by the belt 9 to a drying system, for example a festoon line,not shown. Each of the smoothing rolls 10 con- 5 sists of a wood ormetal core 17 carried on a shaft 19 and provided with a surface orcovering 18 of soft, fibrous material which, in contradistinction to thesteel or steel surfaced rolls'above referred to, are yielding andpervious or absorptive to the aqueous coatings used. I prefer to use acovering of plush which provides a relatively dense, uniform, soft andpervious surface. In place of plush a variety of materials of a fibrousnature, such as various grades of felt, may be used. These rolls may bemounted in adjustable brackets to allow their being moved nearer to orfurther from the coating applying means as may be desirable in applyingdifferent grades or consistencies of aqueous coating mixso ture.

Like the reversely turning steel rolls described in the above-mentionedpatent, my smoothing rolls exert a smoothing action on the coating onthe sheet by picking up a portion of the coating and redepositing it onthe sheet. But apparently due to the character of the surface of myrolls there is little or no tendency for the coating to draw up intoridges such as occurs when an impervious or steel roll is used. Thistendency to draw up into ridges on a rotating smooth impervious roll isa very general phenomenon with liquids, but in the case of suchmaterials as varnish, liquid wax and the like, the ridges also tend toflow out rapidly so that a fairly uniform deposit of coating of suchliquids may result. However, with the coatings used in making coatedpaper,

"which consist of a relatively 'high percentage of insoluble mineralpigments suspended in an aqueous colloidal solution of casein, starch,glue or the like, and which to a degree are gelatinous in character, theridges form on but do not flow out on an impervious roll, andconsequently these ridges are transferred to the paper. In the case ofrolls having a fibrous surface these ridges are much less pronounced. I

= The invention will, therefore, be seen to reside in (l) a method ofcoating paper comprising applying an aqueous coating to a traveling webof paper in contr lied weight and spreading said coating by picking upthe coating and redepositing it upon the traveling web of paper by oneor more cylindrical bodies presenting a fibrous surface and rotatingoppositely to the direction of travel of the paper and preferably at aperipheral speed greater than that of the paper, and (2) in apparatusfor making coated paper comprising means for applying aqueous coatingmixture to a web of paper, means for regulating the weight of coatingapplied, means for advancing the web of paper, and means for smoothingthe coating on the web, said smoothing means comprising one or morerolls covered with or presenting a surface of fibrous material and meansfor rotating said rolls so that the surface thereof in contact with thecoating travels in a direction opposite to that of the paper and at aperipheral speed greater than that of the paper.

I claim:

1. Process of coating paper which comprises picking up aqueous coatingmaterial from a traveling web of paper and redepositing it thereon bymeans of one of more yielding absorptive surfaces moving oppositely tothe direction of travel of the paper.

2. Process of coating paper comprising applying an aqueous coating to atraveling web of paper in controlled weight and spreading said coatingby picking up coating material from and redepositing it upon thetraveling web of paper by means of one or more yielding, absorptivesurfaces moving oppositely to the direction of travel of the paper at aspeed greater than that of the paper.

Patent No. l, 924, 994.

3. Apparatus for making coated paper comprising means for or more rollspresenting a flush surface, and means for rotating said rolls oppositelyto the direction of travel of the paper.

4. Apparatus for coating paper comprising means for applying aqueouscoating mixture to a web of paper, means for regulating the weight ofthe coating applied, means for advancing the web of paper, meansincluding a roll having a yielding, absorptive surface for smoothing thecoating on the web and means for rotating said roll oppositely to thedirection of travel of said web at a peripheral speed greater than thespeed of the web.

travel of the web and at a peripheral speed greater paper.

August 29, 1933.

THEGDORE K. KNAPP, JR.

It is hereby certified that error a patent requiring co'rrec (Seal)ppears in the printed tion as follows:

that the same may conform to the specification of the Page 2, line 82',claim of October, A. D. 1933.

F. M. Hopkins Acting Commissioner of Patents.

